I would start from square one. Turn off the EQ or make it flat again. Listen for a few days to a wide variety of your favorite music. Try to decide if there is anything that consistently sounds "wrong" throughout all your music, either due to your playback hardware or due to your own personal tastes. Then if there is something like that maybe we can find a frequency range that you could boost or cut a little to compensate. I just find it hard to believe that an upside down V will really make everything (except vocals apparently) sound great.